Repeated intravitreal injections of steroids and anti-VEGF agents in the treatment of macular edema, pose potential post-surgical problems. Risk of drug precipitation due to poor solubility;and short vitreal half life upon intravitreal injection are the key deterrents in their delivery. Therefore the broad, long-term objective of this renewal grant application is to develop novel transscleral delivery strategies and to provide non-invasive therapy for macular edema. We propose to combine the prodrug approach with a novel polymeric drug delivery strategy by incorporating these prodrugs into biodegradable surface modified PLGA nanoparticles and thermosensitive PLGA-PEG-PLGA gel. This novel delivery system may provide added stability to steroids and bevacizumab and six-month sustained delivery from a single episcleral administration. Therefore the specific aims of this new grant application are: (1) to determine transscleral permeability of steroids (dexamethasone and prednisolone) and anti-VEGF monoclonal antibody (bevacizumab) (i) alone (ii) encapsulated in unmodified and surface modified nanoparticles (biotin transporter/folate receptor targeted) and (iii) nanoparticles suspended in the thermosensitive gel, using in vitro (ARPE-19 cell line) and ex vivo (isolated sclera and RPE-choroid-sclera) models (2) to synthesize ester-peptide (Valine-, Valine-Valine-, Glycine-Valine-, and Tyrosine-Valine-) prodrugs of dexamethasone and prednisolone targeting peptide transporters present on the basal side of the RPE. We also aim to characterize the physicochemical properties i.e., aqueous solubility, octanol/water partition coefficient, buffer stability and biochemical pharmacology (bioreversion and metabolism) of these compounds in ocular fluids and tissue homogenates including retina/choroid, lens, iris-ciliary body, sclera, vitreous humor and aqueous humor (3) to determine enzymatic stability of steroids, their peptide prodrugs and bevacizumab (i) alone, (ii) encapsulated in unmodified and surface modified nanoparticles and (iii) nanoparticles suspended in the thermosensitive gel, utilizing ocular tissues homogenates i.e. sclera, retina/choroid/Bruch's membrane (4) to evaluate a series of peptide prodrugs of steroids, targeted towards peptide transporters present on the RPE for transscleral delivery (i) alone (ii) encapsulated in unmodified and surface modified nanoparticles and (iii) nanoparticles suspended in the thermosensitive gel using an in vitro (ARPE-19 cell line) and/or ex vivo (isolated sclera and RPE-choroid-sclera) models (5) to evaluate in vivo time and dose dependent ocular bioavailability of steroids and bevacizumab (i) alone (ii) encapsulated in unmodified and surface modified nanoparticles and (iii) nanoparticles suspended in a thermosensitive PLGA-PEG-PLGA gel, following subconjunctival administration, using ocular microdialysis technique in anesthetized and conscious rabbit model. PUBLIC HEALTH RELAVANCE: The broad, long-term objective of this renewal grant application is to develop novel transscleral delivery strategies and to provide non-invasive therapy of steroids (dexamethasone and prednisolone) and anti-VEGF antibody (bevacizumab) for the treatment of macular edema. We propose to combine the prodrug approach with a novel polymeric drug delivery strategy by incorporating these prodrugs into biodegradable surface modified PLGA nanoparticles and thermosensitive PLGA-PEG-PLGA gel. This novel delivery system may provide added stability to steroids and bevacizumab and six-month sustained delivery from a single episcleral administration.